Genetic diversity and phylogenetic relationships among four breeds reared in Sicily using β-lactoglobulin promoter region polymorphisms

The aim of this work was to analyze the genetic diversity and the phylogenetic relationships among the Valle del Belice (VDB) breed and the other sheep breeds considered as ancestors, using -lactoglobulin (BLG) promoter region polymorphisms. The BLG promoter region of 50 randomly chosen animals from the four breeds (VDB n=20; Comisana (COM) n=10; Pinzirita (PIN) n=10; Sarda (SAR) n=10) were sequenced and aligned, and results showed the presence of 36 single nucleotide polymorphisms (SNPs) and one deletion. The number of polymorphic sites identified showed high variability within breeds. Nucleotide (π) and haplotype (Hd) diversity were estimated with DnaSP software, whereas PHASE software was used to infer and analyze haplotypes. A total of 22 haplotypes were found in “best” reconstruction and used for phylogenetic analysis with MEGA software (Neighbor-Joining algorithm). The SAR breed presented the lowest genetic diversity (π=0.00355±0.00151 and Hd=0.279±0.123), whereas the COM breed presented the highest one (π=0.00703±0.00055 and Hd=0.837±0.076). Comparing the nucleotide diversity among breeds, the highest value was obtained between VDB and PIN breeds (π=0.00566), whereas the lowest one between VDB and SAR breeds (π=0.00421). The phylogenetic tree showed the closest relationship between VDB and SAR breeds. Considering that polymorphisms in the BLG promoter region could have a functional role associated with milk composition, the lowest nucleotide diversity between VDB and SAR breeds may be related to a higher similarity of milk composition of these two breeds compared to the others. Further analyses will be conducted on a wider sample in order to confirm the obtained results.